I dont follow you
The doctor doesn't know the theory of relativity thus he assumes that the time on board flows in the same way as on the earth
He assumes also that his brother's heart still beats at 60 beats / minute same as on the earth
If the starcraft is moving away then he expects to receive a pulse every T = 1 + 0.95 = 1.95 sec
Of course the theory of relativity is valid regardless of the doctor's knowledge thus he will actually receive two next signals at a time interval T = 6.24 sec

What is the most natural explanation ?

The pilot's heart frequency on board is lower than on the earth as well as any other metabolic process
Thus the pilot will look younger on his return

No sorry the topic was clear and nett
I claimed that special relativity by itself entails the twin paradox
Joey did not agree

Again a little bit of hystori of physics

The twin paradox had been proposed by Einstein himself before the general relativity
Someone argued that the special relativity may be true , yet the paradox may be false
The reason being that the special relativity is valid only during the cruise phase
What does it happen during acceleration - turning - deceleration ?
In principle the acceleration phase may compensate the cruise phase so that on his return the pilot may have the same age as his twin brother
Nobody knew the answer at the time

This is the key difference between Joey's opinion and mine

I claimed that the paradox is true " Despite " the acceleration - turning - deceleration phases
Joey claimed ( at least this is what I understood ) " Thanks" to the acceleration - turning - deceleration phases

What Joey said is valid to explain why the pilot is younger than his brother on the earth
Why not the other way round ?

The different aging of two twin brothers is however a direct consequence of the relativism of time
If the time flows in a different way on the earth and on the starcraft, why should the two brother alwayes have the same age ?

In other words

Everybody knows that the special relativity claims that it does not make any sense to claim that two events are alwayes simultaneous
or that the same event has alwayes the same duration regardless of the observer
If so
Why should the twin brothers have alwayes the same age ?

NO.

He wouldn't.

If he doesn't know about relativity, he'd expect light to travel with c-v = 0.05c.
That means he expects 20 seconds.
I've written the rest before.
I have tried to be as clear as possible in my post before, but perhaps it wasn't clear enough. Just a "I don't follow you" is hardly helpful to narrow down where things weren't clear. Could you be more precise?

~~~



The problem is that "the twin paradox" itself is ill-defined. What are we talking about?

• The fact that one twin ages more than the other?
  (Everyone agreed on that this is true)
• The idea that there is no "symmetry"?
  (I.e.: One twin ages more than the other, which is because only one stays in an inertial system).

We all agreed on those points and how to solve them, I believe.



Yes, but I don't think anyone disagreed on the fact that the twins are of different age.

We can agree on these points, I believe?

A) Twin A (on earth) is in an inertial system, and what we find calculating in "his" rest frame is valid
B) Twin B (on spaceship) is *NOT* in an inertial system (due to turnaround), and thus we cannot calculate things the same way as we did for Twin A.

The latter point is, I believe, the essence of what gave trouble for MOST of the thread.



~ ~

To summarize, I'm just not sure what we're arguing here.

Why do you assume that my twin studied classic mechanics only ?

He does not know the theory of relativity but he is aware of the Michelson's experiment
My twin stidied also classic electromagnetism
Even Maxwell knew in 19th century that the speed of electromagnetic waves is an invariant

Uhm, I assumed that because you said he didn't know about the theory of relativity.

The fact that c = constant is widely accepted to be one of its postulates. If you don't believe me, then see wikipedia.



Yes, the Maxwell-equations are not invariant under Galilei-transformations, and they provide very strong evidence for why this postulate is a good idea.
Still, going that one step further and realizing that this is actually a fundamental part of nature is what we usually consider a genius move. Something Einstein himself did. Not something just anyone would do.



Setting c=constant and then not doing the rest of special relativity is some sort of "mish-mash" of classical mechanics and the theory of relativity. Sometimes, this mix will provide good results, and sometimes it won't - which can be said for every mix of "correct and wrong" theories to various degrees.

Same mish mash as great scientists such as Lorentz and Poincare did

The twin assumes that his brother is " asleep at the wheel"
He is not
The interpretation of the measures is wrong but the prediction "my brother will look younger than me " is true

Also Lorentz and Poincare and even Maxwell, as you said yourself, kwew that c is a costant but they tried to explain the "light paradox " assuming that Time is absolute

The speed of ligh being a constant entails the relativism of time, ok that's true, but it is not a so straightforward conclusion